Gray scale adjustment method and device for display panel

ABSTRACT

The present invention discloses a gray scale adjustment method and device for a display panel. The method includes: performing an image acquisition on the display panel to obtain a current image; identifying a relationship between a sum of gray scale values of all pixels in the current image and a target value by a distinguishing method, in order to identify an uneven block in the current image; detecting an original output luminance and an original input gray scale of the uneven block; determining a target input gray scale corresponding to a preset target luminance according to an actual gamma curve value obtained by testing the display panel; and taking a difference between the original input gray scale and the target input gray scale as a gray scale compensation value of the uneven block.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national Stage of International ApplicationNo. PCT/CN2018/092942, filed on Jun. 26, 2018, designating the UnitedStates, which claims priority to Chinese Patent Application No.201710497582.2, filed with the Chinese Patent Office on Jun. 26, 2017and entitled “GRAY SCALE ADJUSTMENT METHOD AND DEVICE FOR DISPLAYPANEL”, the content of each of which is hereby incorporated by referencein its entirety.

FIELD

The present application relates to the field of liquid crystal paneldisplay, and more particularly, to a gray scale adjustment method anddevice for a display panel.

BACKGROUND

Due to the complicated production process and difficult control of theliquid crystal panel, unevenness of luminance display (also called muraphenomenon) is likely to occur during the production process, that is, acertain area of the panel is block-shaped which is a trace phenomenondue to the difference in display luminance, reducing the quality levelof the panel. In recent years, with the popularity of TVs such as 2K TVand 4K TV, the unevenness phenomenon has become more and more serious.To solve the unevenness phenomenon, the technique of eliminatingunevenness (also called Demura technology) has emerged at the rightmoment. The technique of eliminating unevenness belongs to a kind ofexternal compensation technology, and currently this technology ismainly to illuminate the backplane, through the CCD (Charge-coupledDevice) optical camera to extract the luminance signal, and detect theunevenness of the display image. Based on the central area of the panel,by comparing the difference between the luminance of the other areas ofthe panel and the central area, and then calculating the display data tobe compensated according to the standard Gamma2.2 curve (the gamma valueof most displays is 2.2), the luminance of the whole panel is uniform.

At present, the technology of eliminating unevenness has the advantagesof simple structure and flexible mode, so it is widely used at thepresent stage. However, the premise of calculating the compensation datais that the panel has already had a standard Gamma2.2 curve, but it isimpossible to achieve precise control of the Gamma curve of each pieceduring the actual production process of the panel, which causes theuneven gray scale compensation value to be inaccurate and easily affectsthe final effect of Demura.

The above content is only used to assist in understanding the technicalsolutions of the present application, and does not constitute anadmission that the above is prior art.

SUMMARY

The main purpose of the present application is to provide a gray scaleadjustment method and device for a display panel, and to solve theproblem that in the process of manufacturing the liquid crystal displaypanel, the uneven (mura) compensation value is not accurate, resultingin poor final effect of elimination of unevenness.

To achieve the above objective, the present application provides a grayscale adjustment method for a display panel. The method includes thefollowing steps:

performing an image acquisition on the display panel to obtain a currentimage;

identifying an uneven block in the current image by using adistinguishing method, and detecting an original output luminance and anoriginal input gray scale of the uneven block, wherein thedistinguishing method is to identify a block of the current image inwhich a sum of gray scale values of all pixels exceeds a target valuerange or identify a block of the current image in which a sum of grayscale values of all pixels is lower than a target value range;

determining a target input gray scale corresponding to a preset targetluminance according to an actual gamma curve value, wherein the actualgamma curve value is obtained by testing the display panel; and

taking a difference between the original input gray scale and the targetinput gray scale as a gray scale compensation value of the uneven block.

Alternatively, before determining the target input gray scalecorresponding to the preset target luminance according to the actualgamma curve value, the method further includes:

obtaining n reference images of the display panel at different inputgray scales, wherein n is an integer greater than or equal to 2.

Alternatively, after obtaining the n reference images of the displaypanel at different input gray scales, the method further includes:calculating a reference gamma curve value of each reference image.

Alternatively, after calculating the reference gamma curve value of eachreference image, the method further includes: taking an average value ofthe reference gamma curve value as the actual gamma curve value.

Alternatively, calculating the reference gamma curve value of eachreference image specifically includes:

detecting a reference input gray scale and a reference output luminanceof each reference image; and

calculating a reference gamma curve value of each reference imageaccording to the reference input gray scale, a reference outputluminance, and a gamma mathematical model.

Alternatively, the gamma mathematical model presents a correspondencebetween the reference input gray scale and the reference outputluminance.

Alternatively, the gamma mathematical model is:

${\frac{{T\; x} - {T\; o}}{{T\; 255} - {T\; o}} = \left( \frac{L\; x}{255} \right)^{Gamma}},$

wherein Tx is the reference output luminance, T255 is a correspondingoutput luminance when the input gray scale is 255, To is a correspondingoutput luminance when the input gray scale is 0, Lx is the referenceinput gray scale, and Gamma is the actual gamma curve value.

Alternatively, the n is an integer greater than or equal to 5.

Alternatively, before determining the target input gray scalecorresponding to the preset target luminance according to the actualgamma curve value, the method further includes:

obtaining an output luminance of a center point of the current image;and

taking the output luminance of the center point of the current image asa preset target luminance.

Alternatively, before determining the target input gray scalecorresponding to the preset target luminance according to the actualgamma curve value, the method further includes:

obtaining the output luminance of each pixel in the area other than theuneven area in the current image.

Alternatively, after the obtaining the output luminance of each pixel inareas other than the uneven area in the current image, the methodfurther includes: taking the average value of the obtained outputluminance as a preset target luminance.

Alternatively, after taking the difference between the original inputgray scale and the target input gray scale as the gray scalecompensation value of the uneven block, the method further includes:

transmitting the gray scale compensation value to the display panel, sothat the display panel adds the gray scale compensation value to theoriginal input gray scale of the uneven block as a new input gray scaleof the uneven block to eliminate the uneven block in the current image.

In addition, in order to achieve the above object, the presentapplication further provides a gray scale adjustment device for adisplay panel, the device including:

an image acquisition module, configured to perform an image acquisitionon the display panel to obtain a current image;

an identification module, configured to identify the uneven block in thecurrent image by using a distinguishing method, and to detect anoriginal output luminance and an original input gray scale of the unevenblock, wherein the distinguishing method is to identify a block of thecurrent image in which a sum of gray scale values of all pixels exceedsa target value range or identify a block of the current image in which asum of gray scale values of all pixels is lower than a target valuerange;

a calculation module, configured to determine a target input gray scalecorresponding to a preset target luminance according to an actual gammacurve value, wherein the actual gamma curve value is obtained by testingthe display panel; and

an adjustment module, configured to take a difference between theoriginal input gray scale and the target input gray scale as a grayscale compensation value of the uneven block.

Alternatively, in the gray scale adjustment device, before determiningthe target input gray scale corresponding to the preset target luminanceaccording to the actual gamma curve value, n reference images of thedisplay panel at different input gray levels are obtained, and the n isan integer greater than or equal to 2.

Alternatively, in the gray scale adjustment device, after obtaining nreference images of the display panel at different input gray levels, areference gamma curve value of each reference image is calculated.

Alternatively, in the gray scale adjustment device, calculating thereference gamma curve value of each reference image specificallyincludes:

detecting a reference input gray scale and a reference output luminanceof each reference image; and

calculating the reference gamma curve value of each reference imageaccording to the reference input gray scale, a reference outputluminance, and a gamma mathematical model.

Alternatively, in the gray scale adjustment device, the gammamathematical model presents a correspondence between the reference inputgray scale and the reference output luminance.

Alternatively, in the gray scale adjustment device, the gammamathematical model is:

${\frac{{T\; x} - {T\; o}}{{T\; 255} - {T\; o}} = \left( \frac{L\; x}{255} \right)^{Gamma}},$

wherein Tx is the reference output luminance, T255 is a correspondingoutput luminance when the input gray scale is 255, To is a correspondingoutput luminance when the input gray scale is 0, Lx is the referenceinput gray scale, and Gamma is the actual gamma curve value.

Alternatively, in the gray scale adjustment device, the n is an integergreater than or equal to 5.

In addition, in order to achieve the above object, the presentapplication further provides a display device including a display paneland a gray scale adjustment device for a display panel as describedabove.

The method for adjusting the gray scale of the display panel proposed inthe present application can compensate the gray scale value of theuneven area of the display panel according to the actual gamma curve andthe preset target luminance during the process of producing each liquidcrystal panel, and eliminate accurately and effectively the unevennessin the display panel, thereby solving the problem that in the process ofmanufacturing the liquid crystal display panel, the uneven (mura)compensation value is not accurate, resulting in poor final effect ofelimination of unevenness.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a conventional acquisitionmethod of a display panel gray scale compensation value.

FIG. 2 is a schematic structural diagram illustrating a gray scaleadjustment device for a display panel of a hardware operatingenvironment according to an embodiment of the present application.

FIG. 3 is a schematic flow chart illustrating a first embodiment of agray scale adjustment method of a display panel according to the presentapplication.

FIG. 4 is a schematic diagram illustrating a principle for eliminatingan uneven area of a display panel according to an embodiment of thepresent application.

FIG. 5 is a schematic diagram illustrating a principle for performingdata compensation on an uneven area of a display panel according to anembodiment of the present application.

FIG. 6 is a schematic flow chart illustrating a second embodiment of agray scale adjustment method of a display panel according to the presentapplication.

FIG. 7 is a schematic block diagram illustrating a gray scale adjustmentmethod of a display panel according to an embodiment of the presentdisclosure.

FIG. 8 is a schematic block diagram illustrating a display deviceaccording to an embodiment of the present application.

The implementation, functional features, and advantages of the presentapplication will be further described with reference to the accompanyingdrawings.

DETAILED DESCRIPTION OF THE INVENTION

It should be understood that the specific embodiments described hereinare merely illustrative of the application and are not intended to limitthe present application.

At present, the technology of eliminating the unevenness (also calledDemura technology) has the advantages of simple structure and flexiblemode, so it is widely used at this stage. However, the premise ofcalculating compensation data is that the panel has already had astandard Gamma 2.2 curve, it is impossible to achieve precise control ofthe Gamma curve of each piece during the actual production process ofthe panel, which causes the uneven gray scale compensation value to beinaccurate and easily affects the final effect of Demura technology. Asshown in FIG. 1, it is the principle of calculating compensation datafor the commonly used Demura technology. As the Gamma curve in FIG. 1,the abscissa is the input gray scale L (i.e., the objective physicalquantity of things), and the ordinate is the output luminance T (i.e.,subjective luminance perception of the human eye). At this stage, inorder to facilitate the calculation, it will assume that this gammacurve is 2.2, the point T in the figure represents the target luminance,and the point R represents the actual luminance of the uneven area. Thenin order to increase the luminance of the uneven area to the targetluminance of the display panel (that is, finally reaching the effect ofobtaining a compensated luminance L1 as shown in the figure), it isnecessary to obtain the compensation gray scale L2 corresponding to theabscissa on the curve of Gamma 2.2. The shortcoming of this approach isthat if the actual Gamma curve of the panel is not 2.2, then thecompensation effect will be biased, and even the uneven (mura)phenomenon will not be improved.

Referring to FIG. 2, FIG. 2 is a schematic structural diagramillustrating a gray scale adjustment device for a display panel in ahardware operating environment according to an embodiment of the presentapplication.

As shown in FIG. 2, the device may include a processor 1001, such as aCPU, a communication bus 1002, a user interface 1003, a camera 1004, anda memory 1005. The communication bus 1002 is used to implementconnection communication between these components. The hardwareinterface 1003 may include a liquid crystal display panel. The camera1004 can be selected as a camera of a high-precision, high-resolutionoptical CCD camera that can achieve the resolution of the human eye. Thememory 1005 may be a high speed RAM memory or a non-volatile memory, andmay include an EEPROM (Electrically Erasable Programmable Read-OnlyMemory).

It will be understood by those skilled in the art that the deviceconfiguration illustrated in FIG. 2 does not constitute a limitation tothe device, and more or less components than those illustrated may beincluded, or some components may be combined, or different componentarrangements may be adopted.

As shown in FIG. 2, the memory 1005 as a computer storage medium mayinclude an operating system, a data storage module, a hardware interfacemodule, and a gray scale adjustment program for the display panel.

In the device shown in FIG. 2, the camera 1004 is configured to performimage acquisition on the display panel. The hardware interface 1003 ismainly used for data interaction with the display panel. The processor1001 and the memory 1005 of the device of the present application may bedisposed in the device. The device may call the gray scale adjustmentprogram for the display panel stored in the memory 1005 by the processor1001, and perform the following operations:

performing an image acquisition on the display panel to obtain a currentimage;

identifying an uneven block in the current image, and detecting anoriginal output luminance and an original input gray scale of the unevenblock;

determining a target input gray scale corresponding to a preset targetluminance according to an actual gamma curve value obtained by testingthe display panel; and

taking a difference between the original input gray scale and the targetinput gray scale as a gray scale compensation value of the uneven block.

Further, the processor 1001 may call the gray scale adjustment programfor the display panel stored in the memory 1005, and further perform thefollowing operations:

obtaining n reference images of the display panel at different inputgray scales, wherein n is an integer greater than or equal to 2;

calculating the reference gamma curve value of each reference image; and

taking an average value of the reference gamma curve value as the actualgamma curve value.

Further, the processor 1001 may call the gray scale adjustment programfor the display panel stored in the memory 1005, and further perform thefollowing operations:

detecting a reference input gray scale and a reference output luminanceof each reference image; and

calculating a reference gamma curve value of each reference imageaccording to the reference input gray scale, a reference outputluminance, and a gamma mathematical model which presents acorrespondence between the reference input gray scale and the referenceoutput luminance.

Further, the processor 1001 may call the gray scale adjustment programfor the display panel stored in the memory 1005, and further perform thefollowing operations:

obtaining an output luminance of a center point of the current image,and taking the output luminance of the center point of the current imageas a preset target luminance.

Further, the processor 1001 may call the gray scale adjustment programfor the display panel stored in the memory 1005, and further perform thefollowing operations:

obtaining the output luminance of each pixel in areas other than theuneven area in the current image; and

taking the average value of the obtained output luminance as a presettarget luminance.

Further, the processor 1001 may call the gray scale adjustment programfor the display panel stored in the memory 1005, and further perform thefollowing operations:

transmitting the gray scale compensation value to the display panel, sothat the display panel adds the gray scale compensation value to theoriginal input gray scale of the uneven block as a new input gray scaleof the uneven block to eliminate the uneven block in the current image.

In the embodiment of the present application, image acquisition isperformed on the display panel to obtain a current image; the unevenblock in the current image is identified, and the original input grayscale and the original output luminance of the uneven block aredetected; a target input gray scale corresponding to a preset targetluminance is determined according to an actual gamma curve value, andthe actual gamma curve value is obtained by testing the display panel;and a difference between the original input gray scale and the targetinput gray scale is taken as a gray scale compensation value of theuneven block. The present embodiment solves the problem that in theprocess of manufacturing the liquid crystal display panel, the uneven(mura) compensation value is not accurate, resulting in poor finaleffect of elimination of unevenness by the technical solution of theembodiment of the present application.

Based on the above hardware configuration, an embodiment of a gray scaleadjustment method for the display panel according to the presentapplication is proposed.

Referring to FIG. 3, FIG. 3 is a schematic flow chart illustrating afirst embodiment of a gray scale adjustment method for a display panelaccording to the present application.

In this embodiment, the method includes the following steps.

At S10, an image acquisition is performed on the display panel to obtaina current image.

It can be understood that the current image is an image currentlydisplayed the display panel.

In a specific implementation, after the display panel is illuminated,the current display image (i.e., the current image) can be captured bythe optical CCD camera.

It should be noted that the display panel in this embodiment may be aliquid crystal display panel, and the liquid crystal display panel canbe applied to a display device such as computer display screen,television display screen, and tablet computer display screen.

At S20, an uneven block in the current image is identified, and anoriginal output luminance and an original input gray scale of the unevenblock are detected.

More specifically, at the process S20, an uneven block in the currentimage is identified by a distinguishing method, and the distinguishingmethod is to identify a block of the current image in which a sum ofgray scale values of all pixels exceeds a target value range or identifya block of the current image in which a sum of gray scale values of allpixels is lower than a target value range.

Through the setting of the target value range, it is possible to reducethe time required for detecting the produced display panel beforeselecting the uneven block, and at the same time, the setting of thetarget value range is accessible by the production end to make theproduction end more flexible to regulate production and testingprocesses.

It should be noted that the luminance signal includes an input grayscale and an output luminance. The input gray scale is a gray scale thatthe display can identify, and the gray scale represents an actualobjective luminance, that is, natural physical quantity of an objectiveobject, and the display will continuously acquire different inputvoltages (also called gamma voltages), and the gray scales reflected bydifferent input voltages are different. The output luminance issubjective luminance perception of the human eye. Since human perceptionof the stimuli from nature is non-linear, the outside world strengthensthe stimuli in a certain proportion. For a human, this stimuli is evenlyincreased. Similarly, the human eye is also nonlinear in perception ofnatural luminance, so the subjective luminance of the people eyeperception is not exactly the same as the actual objective luminance.The gamma curve (i.e., the gamma curve) is used to coordinate themapping relationship between the subjective luminance perception of thehuman eye and the actual objective natural luminance, i.e., tocoordinate the mapping relationship between the output luminance andinput gray scale, and the relationship between them can be determined bya formula: output value=input value^(Gamma).

It can be understood that the output luminance value of the initialdisplay image (i.e., the subjective luminance perception of the humaneye) is known, and the gray scale value of the initially displayed image(i.e., the input gray scale) is also known, but the display screen isdisplayed unevenly under this gray scale, that is, there is unevenness.When detecting the uneven block, some unevenness which is obvious isvisible to the human eye, while some unevenness is not visible to thehuman eye. The professional device detects and identifies the unevenblock in the current image by professional equipment, that is, the pixel(pixel) distribution feature is analyzed according to the display datain the collected current image, and the unevenness is identifiedaccording to the relevant algorithm. There are many related algorithmsin the process of detecting unevenness, which are not limited by theembodiment.

At S30, a target input gray scale corresponding to a preset targetluminance according to an actual gamma curve value is determined, andthe actual gamma curve value is obtained by testing the display panel.

It should be noted that, in this embodiment, there is an even luminancedisplay area in the current image, and the output luminance value of thedisplay area is used as the preset target luminance value.

In a specific implementation, an output luminance of a panel centerpoint of the current image may be obtained, and the output luminance ofthe panel center point may be used as a preset target luminance. Thatis, the output luminance of the current image in a central area of thepanel is obtained, and the central area of the panel is taken as areference so that the luminance of the central area is compared to theluminance of other areas of the panel to get the difference in luminancebetween the central area and the other areas. In the actual productionof the display panel, the center point of the display panel is generallya place with a best optical grade. Therefore, when a panel is to bedebugged, the center point of the panel is generally selected fordebugging.

Alternatively, the output luminance of pixels in areas other than theuneven area in the current image may be obtained, the average value ofthe output luminance of the pixels may be calculated, and the averagevalue of the output luminance may be taken as a preset target luminance.

At S40, a difference between the original input gray scale and thetarget input gray scale is taken as a gray scale compensation value ofthe uneven block.

It can be understood that, referring to FIG. 4, it is assumed that thepicture on the left side illustrates a white block unevenness W and ablack block unevenness B in the horizontal direction. The differencebetween the original (input) gray scale value and the target gray scaleis taken as the compensation data (i.e., the gray scale compensationvalue) of the uneven block by performing the above step S40, and datacompensation is performed on the two regions, that is, the display dataof these regions is the sum of the original display data and thecompensation data, the compensation data of the unevenness of the whiteblock is negative (i.e., the display data will be reduced), and the datacorresponding to unevenness of the black block will be increasedaccordingly, so that even luminance can be obtained finally, andunevenness can be eliminated.

In the specific implementation, referring to FIG. 5, it is assumed thatthe measured actual Gamma curve value of the panel is 2.4. The dottedline is the Gamma 2.4 curve, and the solid line is the Gamma 2.2 curve.It can be seen that the same luminance difference L1 is compensated forthe Gamma 2.2 curve and the Gamma 2.4 curve. The compensated gray scalevalue L3 obtained under the Gamma 2.2 curve is different from thecompensated gray scale value L2 obtained under the Gamma 2.4 curve, thatis, the compensated gray scale values obtained by different Gamma curvesare different, and the compensated gray scale L3 on the Gamma 2.2 curveis smaller than the compensated gray scale value L2 on the actual Gamma2.4 curve, so only compensation that meets the characteristics of thepanel itself is optimal.

After the step S40, the obtained gray scale compensation value may bewritten to an electrically erasable programmable read only memory(EEPROM) to achieve a compensation effect of the current image, that is,the gray scale compensation value is transmitted to the display panel,so that the display panel adds the gray scale compensation value to theoriginal input gray scale of the uneven block as a new input gray of theuneven block to eliminate uneven blocks in the current image (muraphenomenon).

In the process of manufacturing each liquid crystal panel in thisembodiment, the gray scale value compensation is performed on the unevenarea of the display panel according to the actual gamma curve and thepreset target luminance, thereby achieving the most accuratecompensation effect, and the unevenness (mura) is accurately andeffectively eliminated in the display panel.

Referring to FIG. 6, a second embodiment of a gray scale adjustmentmethod for a display panel according to the present invention is basedon the first embodiment of the foregoing method, and FIG. 6 is based onthe embodiment shown in FIG. 3.

In this embodiment, before determining the target input gray scalecorresponding to the preset target luminance according to the actualgamma curve value in the step S30, the method further includes thefollowing steps.

At S01: n reference images of the display panel at different input grayscales is obtained, wherein n is an integer greater than or equal to 2.

In a specific implementation, after the driving circuit lights up thedisplay panel, the initial display state (i.e., the current image) ofthe current display panel can be captured by the high-resolutionresolution CCD camera, the CCD camera additionally captures the imageinformation of the display state of the current display panel atdifferent gray scale values, and the image information of different grayscale values is taken as reference images. Uneven regions in thereference images are identical to the uneven regions of the initialdisplay states (i.e., the current image).

Depending on the actual needs, an original CCD camera may be used totake additional five or more reference images. For example, take fivereference images as an example. These five images are taken by takingfive gray scale values from the image in the front display panel: thefirst image takes a gray scale value of 0, the fifth image takes a grayscale value of 255, and the middle three images take three differentgray scale values. In addition, increasing the number of images takendoes not result in too much work and difficulty, and is simple and easy.

At S02, a reference gamma curve value of each reference image iscalculated.

In this embodiment, the middle three reference images mentioned abovemay be detected to extract corresponding reference input gray scalevalues and reference output luminances. Then a reference gamma curvevalue of each reference image is calculated according to the abovereference input gray scale values, reference output luminances, andgamma mathematical models. The gamma mathematical model presents acorrespondence between the reference input gray scale value and thereference output luminance.

It can be understood that mapping relationship between the input grayscale value of each reference image (that is, it can represent the gammavoltage, i.e., the objective physical quantity of the object computerrecognized) and the output luminance value (i.e., the subjectiveluminance perception of the human eye) is nonlinear (i.e., the gammacurve can reflect this mapping relationship between them, and thismapping relationship can also be called gamma mathematical model). Thisnonlinear mapping relationship may be generally represented by thefollowing formula by default: Output Luminance=Input Gray Scale^(Gamma).It can be seen from the above that the input gray scale value of eachreference image is known. Meanwhile, since the reference image isobtained by a CCD camera, the output luminance value of each referenceimage can be measured, and the output luminance value is also known.Therefore, the gamma value of each reference image can be obtained bythe formula i.e., Output Luminance=Input Gray Scale^(Gamma). The gammavalues of the respective reference images may not be necessarily thesame, and there may be some errors between them.

In a specific implementation, the gamma mathematical model isrepresented by:

${\frac{{T\; x} - {T\; o}}{{T\; 255} - {T\; o}} = \left( \frac{L\; x}{255} \right)^{Gamma}},$

wherein Tx is the reference output luminance, T255 is a correspondingoutput luminance when the input gray scale is 255, To is a correspondingoutput luminance when the input gray scale is 0, Lx is the referenceinput gray scale, and Gamma is the actual gamma curve value.

The embodiment introduces the gamma mathematical model such that thevalue of the gamma curve of each reference image obtained by calculationis closer to the value of the actual gamma curve of the current displaypanel. The gamma curve value of each reference image is calculated bythe above formula, and the error between the calculated result and theactual gamma curve value of the display panel can be further reduced.

At S03, an average value of the reference gamma curve values is taken asthe actual gamma curve value.

It can be understood that, as can be seen from the above, there is anerror in the gamma curve values of each reference image obtained bycalculation, so by obtaining the gamma curve corresponding to theaverage value of their gamma curve values, the gamma curve closet to theactual condition of the panel can be obtained. This gamma curve is takenas the actual gamma curve, and the actual gamma curve is used as areference to find the compensation value actually needed for each unevenregion in the current image of the display panel. In this way, the mostaccurate compensation can be achieved.

In this embodiment, the actual gamma curve of the display panel ismeasured in advance, for example, by taking images of the display panelat different gray scales, combining the gamma mathematical model todetect the reference gamma curve value of the display panel at differentgray scales, and taking the average value of the reference gamma curvevalue as the actual gamma curve value closest to the actual condition ofthe display panel. The actual gamma curve of the display panel can beeffectively obtained during the production of the display panel, therebyenabling to obtain the gray scale compensation value of the uneven areamore precisely.

FIG. 7 is a schematic block diagram illustrating a gray scale adjustmentdevice for a display panel according to an embodiment of the presentdisclosure. The gray scale adjustment device 302 for the display panelincludes the following configuration.

An image acquisition module 10 is configured to perform an imageacquisition on the display panel to obtain a current image.

It can be understood that the current image is the current display imageof the display panel;

In a specific implementation, after the display panel is light, thecurrent display image (i.e., the current image) can be captured by theoptical CCD camera.

It should be noted that the display panel in this embodiment may be aliquid crystal display panel, and the liquid crystal display panel canbe applied to a display device such as a computer display screen, atelevision display screen, and a tablet computer display screen.

An identification module 20 is configured to identify an uneven block inthe current image and detect an original output luminance and anoriginal input gray scale of the uneven block.

It can be understood that unevenness may occur in the current displayimage displayed on the display panel during the process of producing thedisplay panel (that is, there may be an uneven block appearing). Whenthe image of the display panel is acquired, the luminance signal of theuneven block in the current image is extracted.

It should be noted that the luminance signal includes an input grayscale and an output luminance. The input gray scale is a gray scalewhich is identifiable to the display, and the gray scale represents anactual objective luminance, that is, a natural physical quantity of anobjective object. The display will continuously acquire different inputvoltages (also called gamma voltages). The gray scales reflected bydifferent input voltages are different. The output luminance issubjective luminance perception of the human eye. Since human perceptionof the stimuli of nature is non-linear, the outside world strengthensthe stimuli in a certain proportion. For people, this stimuli is evenlyincreased. Similarly, the human eye is also nonlinear in perception ofnatural luminance, so the subjective luminance of the people eyeperception is not exactly the same as the actual objective luminance.The gamma curve (i.e., the gamma curve) is used to coordinate themapping relationship between the subjective luminance perception of thehuman eye and the actual objective natural luminance, i.e., tocoordinate the mapping relationship between the output luminance and theinput gray scale, and the relationship between them can be representedby the formula: Output Value=Input Value^(Gamma).

It can be understood that the output luminance value of the initialdisplay image (i.e., the subjective luminance perception of the humaneye) is known, and the gray scale value of the initially displayed image(i.e., the input gray scale) is also known, but the display screen isdisplayed unevenly under this gray scale, that is, there is unevenness.When detecting the uneven block, some unevenness which is visible to thehuman eye is obvious, which some unevenness is not visible to the humaneye. The professional device detects and identifies the uneven block inthe current image by the machine, that is, the pixel (pixel)distribution feature is analyzed according to the display data in theacquired current image, and the unevenness is identified according tothe relevant algorithm. There are many related algorithms in the processof detecting unevenness, which are not limited by the embodiment.

A calculation module 30 is configured to determine a target input grayscale corresponding to a preset target luminance according to an actualgamma curve value, wherein the actual gamma curve value is obtained bytesting the display panel.

It should be noted that, in this embodiment, there is an even luminancedisplay area in the current image, and the output luminance value of thedisplay area is used as the preset target luminance value.

In a specific implementation, an output luminance of a panel centerpoint of the current image may be obtained, and the output luminance ofthe panel center point may be used as a preset target luminance. Thatis, the output luminance of the current image in a central area of thepanel is obtained, and the central area of the panel is taken as areference so that the luminance of the central area is compared to theluminance of other areas of the panel to get the difference in luminancebetween the central area and the other areas. In the actual productionof the display panel, the center point of the display panel is generallya place with a best optical grade. Therefore, when a panel is to bedebugged, the center point of the panel is generally selected fordebugging.

Alternatively, the output luminance of pixels in areas other than theuneven area in the current image may be obtained, the average value ofthe output luminance of the pixels may be calculated, and the averagevalue of the output luminance may be taken as a preset target luminance.

An adjustment module 40 is configured to take a difference between theoriginal input gray scale and the target input gray scale as a grayscale compensation value of the uneven block.

It can be understood that, referring to FIG. 4, it is assumed that thepicture on the left side illustrates a white block unevenness W and ablack block unevenness B in the horizontal direction. The adjustmentmodule 40 takes the difference between the original (input) gray scalevalue and the target gray scale as the compensation data (i.e., the grayscale compensation value) of the uneven block, and data compensation isperformed on the two regions, that is, the display data of these regionsis the sum of the original display data and the compensation data, thecompensation data of white uneven block is negative (i.e., the displaydata will be reduced), and the data corresponding to the black blockunevenness will be increased accordingly, so that even luminance can beobtained finally, and unevenness can be eliminated.

In the specific implementation, referring to FIG. 5, it is assumed thatthe measured panel actual Gamma curve value is 2.4. The dotted line isthe Gamma 2.4 curve, and the solid line is the Gamma 2.2 curve. It canbe seen that the same luminance difference L1 is compensated for theGamma 2.2 curve and the Gamma 2.4 curve. The compensated gray scalevalue L3 obtained under the Gamma 2.2 curve is different from thecompensated gray scale value L2 obtained under the Gamma 2.4 curve, thatis, the compensated gray scale values obtained by different Gamma curvesare different, and the compensated gray scale L3 on the Gamma2.2 curveis smaller than the compensated gray scale value L2 on the actual Gamma2.4 curve, so only compensation that meets the characteristics of thepanel itself is optimal. Finally, the obtained gray scale compensationvalue is written to an electrically erasable programmable read onlymemory (EEPROM) to realize the compensation effect of the current image,that is, the gray scale compensation value is transmitted to the displaypanel, so that the display panel adds the gray scale compensation valueto the original input grayscale of the uneven block as a new inputgrayscale of the uneven block to the eliminate uneven block in thecurrent image (mura phenomenon).

FIG. 8 is a schematic block diagram illustrating a display deviceaccording to an embodiment of the present application. As shown in thefigure, the display device 300 may include a display panel 301 and agray scale adjustment device 302 for the display panel, and the grayscale adjustment device 302 for the display panel includes:

an image acquisition module 10, configured to perform an imageacquisition on the display panel to obtain a current image;

an identification module 20, configured to identify the uneven block inthe current image by using a distinguishing method, and to detect anoriginal output luminance and an original input gray scale of the unevenblock, wherein the distinguishing method is to identify a block of thecurrent image in which a sum of gray scale values of all pixels exceedsa target value range or identify a block of the current image in which asum of gray scale values of all pixels is lower than a target valuerange;

a calculation module 30, configured to determine a target input grayscale corresponding to a preset target luminance according to an actualgamma curve value, wherein the actual gamma curve value is obtained bytesting the display panel; and

an adjustment module 40, configured to take a difference between theoriginal input gray scale and the target input gray scale as a grayscale compensation value of the uneven block.

In a display device according to an embodiment of the presentapplication, before determining the target input gray scalecorresponding to the preset target luminance according to an actualgamma curve value, n reference images of the display panel at differentinput gray levels may be obtained. The n is an integer greater than orequal to 2.

In a display device according to an embodiment of the presentapplication, after obtaining the n reference images of the display panelat different input gray levels, a reference gamma curve value of eachreference image may be calculated.

In a display device that is further provided by the embodiment of thepresent application, the calculating the reference gamma curve value ofeach reference image specifically includes:

detecting a reference input gray scale and a reference output luminanceof each reference image; and

calculating the reference gamma curve value of each reference imageaccording to the reference input gray scale, a reference outputluminance, and a gamma mathematical model.

In a display device that is further provided by the embodiment of thepresent application, the gamma mathematical model presents acorrespondence between the reference input gray scale and the referenceoutput luminance.

In a display device that is further provided by the embodiment of thepresent application, the gamma mathematical model is:

${\frac{{T\; x} - {T\; o}}{{T\; 255} - {T\; o}} = \left( \frac{L\; x}{255} \right)^{Gamma}},$

wherein Tx is the reference output luminance, T255 is a correspondingoutput luminance when the input gray scale is 255, To is a correspondingoutput luminance when the input gray scale is 0, Lx is the referenceinput gray scale, and Gamma is the actual gamma curve value.

In a display device that is further provided by the embodiment of thepresent application, the n is an integer greater than or equal to 5.

It should be noted that the display panel in this embodiment may be aliquid crystal display panel, and the liquid crystal display panel canbe applied to a display device such as a computer display screen, atelevision display screen, and a tablet computer display screen.

In the process of manufacturing each liquid crystal panel, the grayscale value compensation is performed on the uneven area of the displaypanel according to the actual gamma curve and the preset targetluminance, thereby achieving the most accurate compensation effect, andthe unevenness (mura) is accurately and effectively eliminated in thedisplay panel.

In addition, the embodiment of the present application further providesa computer readable storage medium storing a gray scale adjustmentprogram for the display panel. When the gray scale adjustment programfor the display panel is executed by the processor, the followingoperation are implemented:

performing an image acquisition on the display panel to obtain a currentimage;

identifying an uneven block in the current image, and detecting anoriginal output luminance and an original input gray scale of the unevenblock;

determining a target input gray scale corresponding to a preset targetluminance according to an actual gamma curve value, wherein the actualgamma curve value is obtained by testing the display panel;

taking a difference between the original input gray scale and the targetinput gray scale as a gray scale compensation value of the uneven block.

Further, when the gray scale adjustment program of the display panel isexecuted by the processor, the following operations are alsoimplemented:

obtaining n reference images of the display panel at different inputgray scales, wherein n is an integer greater than or equal to 2;

calculating the reference gamma curve value of each reference image; and

taking an average value of the reference gamma curve value as the actualgamma curve value.

Further, when the gray scale adjustment program of the display panel isexecuted by the processor, the following operations are alsoimplemented:

detecting a reference input gray scale and a reference output luminanceof each reference image; and

calculating a reference gamma curve value of each reference imageaccording to the reference input gray scale, a reference outputluminance, and a gamma mathematical model, wherein the gammamathematical model presents a correspondence between the reference inputgray scale and the reference output luminance.

Further, when the gray scale adjustment program of the display panel isexecuted by the processor, the following operation is also implemented:

obtaining an output luminance of a center point of the current image,and taking the output luminance of the center point of the current imageas a preset target luminance.

Further, when the gray scale adjustment program of the display panel isexecuted by the processor, the following operations are alsoimplemented:

obtaining the output luminance of each pixel in the area other than theuneven area in the current image; and

calculating an average value of the output luminances of the pixel, andtaking the average value of the obtained output luminance as a presettarget luminance.

Further, when the gray scale adjustment program of the display panel isexecuted by the processor, the following operation is also implemented:

transmitting the gray scale compensation value to the display panel, sothat the display panel adds the gray scale compensation value to theoriginal input gray scale of the uneven block as a new input gray scaleof the uneven block to eliminate the uneven block in the current image.

In the embodiment, by capturing the image of the display panel atdifferent gray levels, and combining the gamma mathematical model, thegamma curve value of the display panel at different gray levels isdetected, and the average value of the gamma curve value is taken as theclosest to the actual state of the display panel. The actual gamma curveof the display panel can be effectively obtained during the productionof the display panel, thereby enabling to obtain the gray scalecompensation value of the uneven area more precisely, which solves theproblem that the effect of eliminating the unevenness is not good sincethe unevenness compensation value is not accurate enough in the processof manufacturing a liquid crystal display panel.

It should be noted that the term “include”, “comprising”, or any othervariants thereof is intended to encompass a non-exclusive inclusion,such that a process, method, article, or system that includes aplurality of elements not only includes those elements, but alsoincludes other elements that are not explicitly listed, or elements thatare inherent to such a process, method, item, or system. Without furtherlimitation, an element defined by the phrase “comprising a . . . ” doesnot exclude the presence of additional equivalent elements in theprocess, method, item, or system which include the element.

The serial numbers of the embodiments of the present application aremerely for the description, and do not represent the advantages anddisadvantages of the embodiments.

Through the description of the above embodiments, those skilled in theart can clearly understand that the foregoing embodiment method can beimplemented by means of software plus a necessary general hardwareplatform, and of course, can also be through hardware, but in manycases, the former is better. Based on such understanding, the technicalsolution of the present application, which is essential or contributesto the prior art, may be embodied in the form of a software productstored in a storage medium (such as ROM/RAM, disk, optical disc)including a plurality of instructions for enabling a terminal device(which may be a mobile phone, a computer, a server, an air conditioner,or a network device, etc.) to perform the method described in thevarious embodiments of the present application.

The above is only preferred embodiments of the present application, andthus does not limit the scope of the patent application, and theequivalent structure or equivalent process transformation made by thespecification and the drawings of the present application, or directlyor indirectly applied to other related technical fields should beincluded in the scope of patent protection of this application.

The invention claimed is:
 1. A gray scale adjustment method for adisplay panel, comprising: performing an image acquisition on thedisplay panel to obtain a current image; identifying an uneven block inthe current image by using a distinguishing method, and detecting anoriginal output luminance and an original input gray scale of the unevenblock, wherein the distinguishing method includes either (a) identifyinga block of the current image in which a sum of gray scale values of allpixels exceeds a target value range or (b) identifying a block of thecurrent image in which a sum of gray scale values of all pixels is lowerthan a target value range; determining a target input gray scalecorresponding to a preset target luminance according to an actual gammacurve value, wherein the actual gamma curve value is obtained by testingthe display panel; taking a difference between the original input grayscale and the target input gray scale as a gray scale compensation valueof the uneven block; and transmitting the gray scale compensation valueto the display panel, so that the display panel adds the gray scalecompensation value to the original input gray scale of the uneven blockas a new input gray scale of the uneven block to eliminate the unevenblock in the current image.
 2. The method according to claim 1, whereinbefore determining the target input gray scale corresponding to thepreset target luminance according to the actual gamma curve value, themethod further includes: obtaining n reference images of the displaypanel at different input gray scales, wherein the n is an integergreater than or equal to
 2. 3. The method according to claim 2, whereinafter obtaining the n reference images of the display panel at differentinput gray scales, the method further includes: calculating a referencegamma curve value of each reference image.
 4. The method according toclaim 3, wherein after calculating the reference gamma curve value ofeach reference image, the method further includes: taking an averagevalue of the reference gamma curve value as the actual gamma curvevalue.
 5. The method according to claim 4, wherein calculating thereference gamma curve value of each reference image includes: detectinga reference input gray scale and a reference output luminance of eachreference image; calculating the reference gamma curve value of eachreference image according to the reference input gray scale, a referenceoutput luminance, and a gamma mathematical model.
 6. The methodaccording to claim 5, wherein the gamma mathematical model presents acorrespondence between the reference input gray scale and the referenceoutput luminance.
 7. The method according to claim 6, wherein the gammamathematical model is:${\frac{{T\; x} - {T\; o}}{{T\; 255} - {T\; o}} = \left( \frac{L\; x}{255} \right)^{Gamma}},$wherein Tx is the reference output luminance, T255 is a correspondingoutput luminance when the input gray scale is 255, To is a correspondingoutput luminance when the input gray scale is 0, Lx is the referenceinput gray scale, and Gamma is the actual gamma curve value.
 8. Themethod according to claim 2, wherein the n is an integer greater than orequal to
 5. 9. The method according to claim 2, wherein beforedetermining the target input gray scale corresponding to the presettarget luminance according to the actual gamma curve value, the methodfurther includes: obtaining an output luminance of a center point of thecurrent image, and taking the output luminance of the center point ofthe current image as a preset target luminance.
 10. The method accordingto claim 2, wherein before determining the target input gray scalecorresponding to the preset target luminance according to the actualgamma curve value, the method further includes: obtaining outputluminance of each pixel in areas other than the uneven area in thecurrent image.
 11. The method according to claim 10, wherein after theobtaining the output luminance of each pixel in the areas other than theuneven area in the current image, the method further includes: takingthe average value of the obtained output luminance as a preset targetluminance.
 12. A gray scale adjustment device for a display panel,comprising a processor, and a memory coupled to the processor andincluding instructions to cause the processor to perform operationscomprising: performing an image acquisition on the display panel toobtain a current image; identifying an uneven block in the current imageby using a distinguishing method, and detecting an original outputluminance and an original input gray scale of the uneven block, whereinthe distinguishing method includes (a) identifying a block of thecurrent image in which a sum of gray scale values of all pixels exceedsa target value range or (b) identifying a block of the current image inwhich a sum of gray scale values of all pixels is lower than a targetvalue range; determining a target input gray scale corresponding to apreset target luminance according to an actual gamma curve value,wherein the actual gamma curve value is obtained by testing the displaypanel; and to taking a difference between the original input gray scaleand the target input gray scale as a gray scale compensation value ofthe uneven block and transmitting the gray scale compensation value tothe display panel, wherein the display panel adds the gray scalecompensation value to the original input gray scale of the uneven blockas a new input gray scale of the uneven block to eliminate the unevenblock in the current image.
 13. The gray scale adjustment deviceaccording to claim 12, wherein before determining the target input grayscale corresponding to the preset target luminance according to theactual gamma curve value, n reference images of the display panel atdifferent input gray levels is obtained, and the n is an integer greaterthan or equal to
 2. 14. The gray scale adjustment device according toclaim 13, wherein after obtaining the n reference images of the displaypanel at different input gray levels, a reference gamma curve value ofeach reference image is calculated.
 15. The gray scale adjustment deviceaccording to claim 14, wherein calculating the reference gamma curvevalue of each reference image specifically includes: detecting areference input gray scale and a reference output luminance of eachreference image; and calculating the reference gamma curve value of eachreference image according to the reference input gray scale, a referenceoutput luminance, and a gamma mathematical model.
 16. The gray scaleadjustment device according to claim 15, the gamma mathematical modelcharacterizing a correspondence between the reference input gray scaleand the reference output luminance.
 17. The gray scale adjustment deviceaccording to claim 16, wherein the gamma mathematical model is:${\frac{{T\; x} - {T\; o}}{{T\; 255} - {T\; o}} = \left( \frac{L\; x}{255} \right)^{Gamma}},$wherein Tx is the reference output luminance, T255 is a correspondingoutput luminance when the input gray scale is 255, To is a correspondingoutput luminance when the input gray scale is 0, Lx is the referenceinput gray scale, and Gamma is the actual gamma curve value.
 18. Thegray scale adjustment device according to claim 13, wherein the n is aninteger greater than or equal to
 5. 19. A display device, comprising: adisplay panel; and a gray scale adjustment device for a display panelaccording to claim 12.